1. Field of the Invention
The invention is generally related to valve seat refitting tools and in particular to an apparatus used primarily to cut safety valve seats for reuse is high pressure vessels.
2. General Background
In high pressure situations safety valves open and close frequently. This results in foreign materials being trapped between the valve and valve seat which chip or dent the valve seat, causing leakage and eventual erosion. To maintain proper sealing, the valve seat must be recut to fit tightly with the valve. Apparatus known for cutting or refinishing nozzles and valve seats include the following.
U.S. Pat. No. 4,090,805 issued to E. E. Grimsley entitled "Cutting Tool For Removing Governor Chest Nozzles And Refinishing The Nozzle Seats" discloses a portable cutting tool that rotates and axially advances two (2) symetrically positioned cutting blades that cut away weld material in annular overlapping paths. A second cutting head is provided for refinishing the nozzles seats after the nozzles have been removed.
U.S. Pat. No. 2,393,361 issued to E. G. A. Flodman entitled "Pin Drill And End Mill" discloses symetrically positioned cutting blades.
U.S. Pat. No. 4,178,115 issued to J. L. Pool, U.S. Pat. No. 4,626,143 issued to D. C. Rembold, U.S. Pat. No. 3,901,619 issued to V. A. Scritchfield, U.S. Pat. No. 611,254 issued to A. R. Jackson, U.S. Pat. No. 3,088,202 issued to R. J. Murray, U.S. Pat. No. 2,428,099 issued to L. A. Smith and U.S. Pat. No. 4,147,462 issued to J. R. Appleby, et al. teach valve seat refinishing tools and are representative of the state of the technology in this field.
Although the present state of the art provides a variety of cutting tools, what is needed is a tool which is adjustable to fit a variety of sizes and capable of cutting three (3) faces of the valve seat at the same time.